https://www.quantumechanics.com\
This is the unit I had installed and I'm very happy with it!
Tired of listening to your engine rev itself to death on the highway? Can’t find an overdrive transmission that you know will work and not cost you thousands of dollars to rebuild? (Aside from being 30 to 50 years old, with 50 to 70 year old technology!) After many years of development, we can now offer a complete 5 speed conversion kit package for the Triumph TR series cars. This kit comes complete with a modified, rebuilt Ford type 9 (Sierra) 5 speed transmission with the standard Ford gear ratios and a one year warranty. It also includes a new driveshaft, new transmission rear flange, new cast aluminum bell housing, new engine pilot bushing, transmission mount kit, modified TR shifter to fit the Ford transmission, new speedometer cable, new clutch disk, and all hardware and instructions to install it in your car. You need to specify the year and model of your car and what year is your engine. (They are not always the same as the car’s year anymore!) This kit may require some exhaust modifications for the TR2/3 and early TR4 cars, depending on the type and manufacturer of your exhaust system. Other than that it is a bolt in conversion. You reuse your flywheel, clutch components, starter, slave cylinder and all other stock components. The speedometer must be recalibrated. The kit requires no cutting of sheet metal and is totally reversible if you ever want to put the original transmission back in the car